Intro to Motion - 8th grade physical science

Physical Science - intro to motion

1. Unit 2: Motion

2. Motion

3. Describing Motion To describe motion, you need to state the direction as well as how fast an object is moving. Motion is a change of position

4. Frame of Reference A frame of reference is something that is not moving with respect to the observer that can be used to detect motion Necessary to describe motion What are you/the object moving IN RELATION TO? AKA - an object that you use to tell if you are moving

5. Relative Motion Relative motion is the movement in relation to a frame of reference E.g., the subway is moving at 17 mph in relation to the platform, but the people inside are not moving in relation to the subway seats.

6. QUESTION (answer in PearDeck): The dog IS MOVING in relation to...

7. QUESTION (answer in PearDeck): The dog is NOT MOVING in relation to...

8. QUESTION (answer in PearDeck): The person is NOT MOVING in relation to...

9. QUESTION (answer in PearDeck): The person IS MOVING in relation to...

10. QUESTION (answer in PearDeck): Describe a frame of reference in which the people are moving. If you need help getting started, try this sentence starter: They are moving in relation to ___________________

11. QUESTION (answer in PearDeck): Describe a frame of reference in which the people are not moving. If you need help getting started, try this sentence starter: They are not moving in relation to ___________________

12. Answer in Pear Deck : What do you know about the words “distance” and “displacement”? How might they be related to the unit? If you aren’t sure, make a guess.

13. Distance and Displacement

14. Vector vs. Scalar Quantities (numbers/measurements) can be either scalar or vector quantities. Scalar = a quantity described just by magnitude (amount/number) Ex: 6 feet, 2 meters, 173 centimeters Vector = a quantity described by magnitude and direction Ex: 6 feet tall, 2 meters west, 173 centimeters to the right ANYTHING THAT HAS A DIRECTION IS A VECTOR

15. Distance vs. Displacement Distance = the length of the path traveled between two points Standard unit for distance is meters Displacement = the straight line between start and end point (including direction) Displacement is an example of a vector E.g., What would you displacement be if you rode a rollercoaster?

16. If you’re still iffy on the difference between distance and displacement, watch this!

17. Combining Displacements

18. Combining Displacements

19. Displacement Practice 1 Amy runs 2 miles south, then turns around and runs 3 miles north. What distance did Amy travel? What is her displacement?

20. Displacement Practice 2 2. Jermaine runs exactly 2 laps around a 400 meter track. Your answer should be in meters. What distance did Jermaine travel? What is his displacement?

21. Speed and Velocity

22. Speed Speed = the rate in which something moves (distance traveled in a certain time) Standard unit is meters/second (m/s) QUESTION (answer in PearDeck): What are some other units of speed?

23. Instantaneous vs. Average Speed Instantaneous Speed - speed measured at one moment Average Speed - calculated over an entire trip Both must have UNITS!

24. QUESTION (answer in PearDeck): All cars have a speedometer. What kind of speed does it measure? What units does it typically have?

25. Average Speed Average Speed - speed calculated over an entire trip QUESTION (answer in PearDeck): Why might it be useful to know your average speed?

26. A person jogs 4.0 km in 32 minutes, then 2.0 km in 22 minutes, and finally 1.0 km in 16 minutes. What is the jogger’s average speed? Step 1 - Add up distances: 4.0km + 2.0 km + 1.0km = 7.0km Step 2 - Add up times: 32min + 22 minutes + 16 minutes = 70 minutes Step 3 - Substitute: 7.0km / 70 minutes Step 4 - Divide: 7/ 70 = 0.1 Step 5 - Include UNITS: 0.1 km/minutes

27. Practice -- use paper to show your work! A train travels 190 km in 3.0 hours, and then 120 km in 2.0 hours. What is its average speed? While on vacation, you measure the times and distances you traveled. You travel 35 km in 0.4 hours, followed by 53 km in 0.6 hours. What is your average speed?

28. Check your answers A train travels 190 km in 3.0 hours, and then 120 km in 2.0 hours. What is its average speed? 62 km/hour While on vacation, you measure the times and distances you traveled. You travel 35 km in 0.4 hours, followed by 53 km in 0.6 hours. What is your average speed? 88 km/hour

29. In one minute, write the most important thing from today’s lesson.

30. Velocity Sometimes, knowing the speed of an object isn’t enough! Velocity = speed and direction Velocity is a VECTOR A change of velocity can occur if the object changes speed or direction You can use v = d/t to solve velocity problems in the same way you used speed = total distance/total time

31. Acceleration

32. Acceleration = a change in velocity

33. Acceleration The rate at which velocity changes is called acceleration. Acceleration is a vector - what does this mean? Acceleration can be a change of speed, a change of direction, or both! Speeding up, slowing down, or changing direction Examples?

34. Velocity Calculations

35. Example 1 - What is the velocity of a car that travels 100.0 meters, northeast in 4.65 seconds? Looking for : Velocity of the car ( v ) Solution(plug in what you know!) The velocity of the car is 21.5 meters per second, northeast. Given Distance = 100.0 meters Time = 4.65 seconds Relationship/Equation :

36. Example 2 - A boat travels with a velocity equal to 14.0 meters per second, east in 5.15 seconds. What distance in meters does the boat travel? Looking for :Distance the boat travels. ( d ) Solution (plug in what you know!) How do you solve ratios? Isolate the variable (cross multiply OR use inverse operations) 72.1 m = d The boat traveled 72.1 meters to the eas t Given Velocity = 14.0 meters per second, east Time = 5.15 seconds Relationship/Equation:

37. Acceleration Practice Acceleration = change in velocity/total time f inal velocity - initial (starting) velocity / time A car traveling NW at 10m/s starts to slow down. It comes to a complete stop after 20 seconds. What is its acceleration? A ball was rolling on the ground with a velocity of 5 m/s to the left. It then reaches a hill and slows down to 2 m/s. This took a total of 3 seconds. What is its acceleration? A sprinter accelerated from the starting block to a speed of 8.0 m/s in 4 seconds. What is the magnitude of the acceleration?

38. Acceleration Practice Acceleration = change in velocity/total time final velocity - initial (starting) velocity / time A car traveling NW at 10m/s starts to slow down. It comes to a complete stop after 20 seconds. What is its acceleration? ( -0.5 m/s 2 ) A ball was rolling on the ground with a velocity of 5 m/s to the left. It then reaches a hill and slows down to 2 m/s. This took a total of 3 seconds. What is its acceleration? (-1m/s 2 ) A sprinter accelerated from the starting block to a speed of 8.0 m/s in 4 seconds. What is the magnitude of the acceleration? (2.0 m/s 2 )

39. What it measures Scalar (magnitude only) or Vector (magnitude and direction) Formula Possible Units Distance Length of a path Scalar Add up all of paths traveled meters (m), feet (ft), inches (in), miles, kilometer Displacement Distance and direction (in a straight line) between start and end Vector Measure straight line from start to end meters (m), feet (ft), inches (in), miles, kilometer AND direction Speed How much distance an object covers in a certain time Scalar ( Total distance)/(total time) meters/second (m/s), inches/ minus , miles/hour (mph) Velocity Speed and direction of an object Vector meters/second (m/s), inches/minus, miles/hour (mph) AND directions Acceleration The rate at which velocity changes Vector meters/second 2 (m/s 2 )

40. What it measures Scalar or Vector Formula/How to find Possible Units Distance Displacement Speed Velocity Acceleration